Method and apparatus for RACH procedure in wireless systems

ABSTRACT

A method of user equipment (UE) for random access operation in a wireless communication system is provided. The method comprises receiving, from a base station (BS), random access channel (RACH) configuration information including RACH chunk information corresponding to at least one antenna beam including a beam identifier (ID), determining a RACH chunk based on the RACH configuration information received from the BS, transmitting, to the BS, a RACH preamble on the determined RACH chunk according to the RACH configuration information associated with the beam ID, and receiving, from the BS, a RACH response (RAR) corresponding to the transmitted RACH preamble and a downlink channel for a RAR transmission, wherein a random access-radio network temporary identification (RA-RNTI) is calculated based on an index of a slot and an index of the RACH chunk on which the RACH preamble is transmitted.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/432,393, filed on Dec. 9, 2016. The content ofthe above-identified patent document is incorporated herein byreference.

TECHNICAL FIELD

The present application relates generally to random access operation inwireless communication systems. More specifically, this disclosurerelates to random access channel procedures of multi-beam operation inwireless communication systems.

BACKGROUND

5th generation (5G) mobile communications, initial commercialization ofwhich is expected around 2020, is recently gathering increased momentumwith all the worldwide technical activities on the various candidatetechnologies from industry and academia. The candidate enablers for the5G mobile communications include massive antenna technologies, fromlegacy cellular frequency bands up to high frequencies, to providebeamforming gain and support increased capacity, new waveform (e.g., anew radio access technology (RAT)) to flexibly accommodate variousservices/applications with different requirements, new multiple accessschemes to support massive connections, and so on. The InternationalTelecommunication Union (ITU) has categorized the usage scenarios forinternational mobile telecommunications (IMT) for 2020 and beyond into 3main groups such as enhanced mobile broadband, massive machine typecommunications (MTC), and ultra-reliable and low latency communications.In addition, the ITC has specified target requirements such as peak datarates of 20 gigabit per second (Gb/s), user experienced data rates of100 megabit per second (Mb/s), a spectrum efficiency improvement of 3×,support for up to 500 kilometer per hour (km/h) mobility, 1 millisecond(ms) latency, a connection density of 106 devices/km2, a network energyefficiency improvement of 100× and an area traffic capacity of 10Mb/s/m2. While all the requirements need not be met simultaneously, thedesign of 5G networks may provide flexibility to support variousapplications meeting part of the above requirements on a use case basis.

SUMMARY

The present disclosure relates to a pre-5th-Generation (5G) or 5Gcommunication system to be provided for supporting higher data ratesbeyond 4th-Generation (4G) communication system such as long termevolution (LTE). Embodiments of the present disclosure provide multipleservices in advanced communication systems.

In one embodiment, a user equipment (UE) for random access operation ina wireless communication system is provided. The UE comprises at leastone transceiver configured to receive, from a base station (BS), randomaccess channel (RACH) configuration information including RACH chunkinformation corresponding to at least one antenna beam including a beamidentifier (ID) and at least one processor configured to determine anRACH chunk based on the RACH configuration information received from theBS. The transceiver is further configured to transmit, to the BS, anRACH preamble on the determined RACH chunk according to the RACHconfiguration information associated with the beam ID and receive, fromthe BS, an RACH response (RAR) corresponding to the transmitted RACHpreamble, a random access-radio network temporary identification(RA-RNTI) of a downlink channel for an RAR transmission being calculatedbased on an index of a slot and an index of the RACH chunk on which theRACH preamble is transmitted.

In another embodiment, a base station (BS) for random access operationin a wireless communication system is provided. The BS comprises atleast one processor configured to determine random access channel (RACH)configuration information including RACH chunk. The BS further comprisesat least one transceiver configured to transmit, to a user equipment(UE), the RACH configuration information including RACH chunkinformation corresponding to at least one antenna beam including a beamidentifier (ID), receive, from the UE, an RACH preamble on the RACHchunk according to the RACH configuration information associated withthe beam ID, and transmit, to the UE, an RACH response (RAR)corresponding to the received RACH preamble, wherein a randomaccess-radio network temporary identification (RA-RNTI) of a downlinkchannel for an RAR transmission is calculated based on an index of aslot and an index of the RACH chunk on which the RACH preamble isreceived.

In yet another embodiment, a method of user equipment (UE) for randomaccess operation in a wireless communication system is provided. Themethod comprises receiving, from a base station (BS), random accesschannel (RACH) configuration information including RACH chunkinformation corresponding to at least one antenna beam including a beamidentifier (ID), determining an RACH chunk based on the RACHconfiguration information received from the BS, transmitting, to the BS,an RACH preamble on the determined RACH chunk according to the RACHconfiguration information associated with the beam ID, and receiving,from the BS, an RACH response (RAR) corresponding to the transmittedRACH preamble and a downlink channel for an RAR transmission. Ae randomaccess-radio network temporary identification (RA-RNTI) is calculatedbased on an index of a slot and an index of the RACH chunk on which theRACH preamble is transmitted.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure;

FIG. 2 illustrates an example eNB according to embodiments of thepresent disclosure;

FIG. 3 illustrates an example UE according to embodiments of the presentdisclosure;

FIG. 4A illustrates an example high-level diagram of an orthogonalfrequency division multiple access transmit path according toembodiments of the present disclosure;

FIG. 4B illustrates an example high-level diagram of an orthogonalfrequency division multiple access receive path according to embodimentsof the present disclosure;

FIG. 5 illustrates an example network slicing according to embodimentsof the present disclosure;

FIG. 6 illustrates an example number of digital chains according toembodiments of the present disclosure;

FIG. 7 illustrates an example random access procedures according toembodiments of the present disclosure;

FIG. 8A illustrates an example RACH occasion according to embodiments ofthe present disclosure;

FIG. 8B illustrates another example RACH occasion according toembodiments of the present disclosure;

FIG. 8C illustrates an example RACH symbols according to embodiments ofthe present disclosure;

FIG. 9A illustrates an example RACH channel structure according toembodiments of the present disclosure;

FIG. 9B illustrates another example RACH channel structure according toembodiments of the present disclosure;

FIG. 9C illustrates yet another example RACH channel structure accordingto embodiments of the present disclosure;

FIG. 10A illustrates an example RACH chunk according to embodiments ofthe present disclosure;

FIG. 10B illustrates another example RACH chunk according to embodimentsof the present disclosure;

FIG. 11 illustrates an example RAR occasion according to embodiments ofthe present disclosure; and

FIG. 12 illustrates a flow chart of a method for RACH procedureaccording to embodiments of the present disclosure

DETAILED DESCRIPTION

FIG. 1 through FIG. 12, discussed below, and the various embodimentsused to describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The following documents are hereby incorporated by reference into thepresent disclosure as if fully set forth herein: 3GPP TS 36.211 v13.0.0,“E-UTRA, Physical channels and modulation;” 3GPP TS 36.212 v13.0.0,“E-UTRA, Multiplexing and Channel coding;” 3GPP TS 36.213 v13.0.0,“E-UTRA, Physical Layer Procedures;” 3GPP TS 36.331 v13.0.0, “RadioResource Control (RRC) Protocol Specification;” 3GPP TS 36.321 v13.0.0,“E-UTRA, Medium Access Control (MAC) protocol specification;” and 3GPPTS 36.331 v13.0.0, “E-UTRA, Radio Resource Control (RRC) ProtocolSpecification.”

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a “beyond 4G network” or a“post LTE system.”

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission coverage, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques and the like arediscussed in 5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul communication, moving network,cooperative communication, coordinated multi-points (CoMP) transmissionand reception, interference mitigation and cancellation and the like.

In the 5G system, hybrid frequency shift keying and quadrature amplitudemodulation (FQAM) and sliding window superposition coding (SWSC) as anadaptive modulation and coding (AMC) technique, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

FIGS. 1-4B below describe various embodiments implemented in wirelesscommunications systems and with the use of orthogonal frequency divisionmultiplexing (OFDM) or orthogonal frequency division multiple access(OFDMA) communication techniques. The descriptions of FIGS. 1-3 are notmeant to imply physical or architectural limitations to the manner inwhich different embodiments may be implemented. Different embodiments ofthe present disclosure may be implemented in any suitably-arrangedcommunications system.

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure. The embodiment of the wireless network shownin FIG. 1 is for illustration only. Other embodiments of the wirelessnetwork 100 could be used without departing from the scope of thisdisclosure.

As shown in FIG. 1, the wireless network includes an eNB 101, an eNB102, and an eNB 103. The eNB 101 communicates with the eNB 102 and theeNB 103. The eNB 101 also communicates with at least one network 130,such as the Internet, a proprietary Internet Protocol (IP) network, orother data network.

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business (SB); a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); aUE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M), such as a cell phone, a wireless laptop, a wirelessPDA, or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 maycommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, WiFi, or other wireless communication techniques.

Depending on the network type, the term “base station” or “BS” can referto any component (or collection of components) configured to providewireless access to a network, such as transmit point (TP),transmit-receive point (TRP), an enhanced base station (eNodeB or eNB),a 5G base station (gNB), a macrocell, a femtocell, a WiFi access point(AP), or other wirelessly enabled devices. Base stations may providewireless access in accordance with one or more wireless communicationprotocols, e.g., 5G 3GPP new radio interface/access (NR), long termevolution (LTE), LTE advanced (LTE-A), high speed packet access (HSPA),Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “BS”and “TRP” are used interchangeably in this patent document to refer tonetwork infrastructure components that provide wireless access to remoteterminals. Also, depending on the network type, the term “userequipment” or “UE” can refer to any component such as “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” “receivepoint,” or “user device.” For the sake of convenience, the terms “userequipment” and “UE” are used in this patent document to refer to remotewireless equipment that wirelessly accesses a BS, whether the UE is amobile device (such as a mobile telephone or smartphone) or is normallyconsidered a stationary device (such as a desktop computer or vendingmachine).

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of the UEs 111-116include circuitry, programming, or a combination thereof, for efficientCSI reporting on PUCCH in an advanced wireless communication system. Incertain embodiments, and one or more of the eNBs 101-103 includescircuitry, programming, or a combination thereof, for receivingefficient CSI reporting on PUCCH in an advanced wireless communicationsystem.

Although FIG. 1 illustrates one example of a wireless network, variouschanges may be made to FIG. 1. For example, the wireless network couldinclude any number of eNBs and any number of UEs in any suitablearrangement. Also, the eNB 101 could communicate directly with anynumber of UEs and provide those UEs with wireless broadband access tothe network 130. Similarly, each eNB 102-103 could communicate directlywith the network 130 and provide UEs with direct wireless broadbandaccess to the network 130. Further, the eNBs 101, 102, and/or 103 couldprovide access to other or additional external networks, such asexternal telephone networks or other types of data networks.

FIG. 2 illustrates an example eNB 102 according to embodiments of thepresent disclosure. The embodiment of the eNB 102 illustrated in FIG. 2is for illustration only, and the eNBs 101 and 103 of FIG. 1 could havethe same or similar configuration. However, eNBs come in a wide varietyof configurations, and FIG. 2 does not limit the scope of thisdisclosure to any particular implementation of an eNB.

As shown in FIG. 2, the eNB 102 includes multiple antennas 205 a-205 n,multiple RF transceivers 210 a-210 n, transmit (TX) processing circuitry215, and receive (RX) processing circuitry 220. The eNB 102 alsoincludes a controller/processor 225, a memory 230, and a backhaul ornetwork interface 235.

The RF transceivers 210 a-210 n receive, from the antennas 205 a-205 n,incoming RF signals, such as signals transmitted by UEs in the network100. The RF transceivers 210 a-210 n down-convert the incoming RFsignals to generate IF or baseband signals. The IF or baseband signalsare sent to the RX processing circuitry 220, which generates processedbaseband signals by filtering, decoding, and/or digitizing the basebandor IF signals. The RX processing circuitry 220 transmits the processedbaseband signals to the controller/processor 225 for further processing.

In some embodiments, the RF transceiver 210 a-201 n is capable oftransmitting, to a user equipment (UE), the RACH configurationinformation including RACH chunk information corresponding to at leastone antenna beam including a beam identifier (ID) and an RACH response(RAR) corresponding to the received RACH preamble, wherein a randomaccess-radio network temporary identification (RA-RNTI) of a downlinkchannel for an RAR transmission is calculated based on an index of aslot and an index of the RACH chunk on which the RACH preamble isreceived.

In some embodiments, the RF transceiver 210 a-201 n is capable ofreceiving the RACH preamble based on an RACH occasion by re-selecting,by the UE, other RACH chunks each of which includes RACH symbols basedon the RACH chunk information or performing, by the UE, a power rampingthat adjusts a transmit power of the RACH preamble. In such embodiments,the RACH configuration information comprises at least one of the indexof the slot, the index of the RACH chunk, partitioning information, beamsweeping information, a preamble type, or retransmission information.

In some embodiments, the RF transceiver 210 a-201 n is capable ofreceiving the RACH preamble on dedicated resources over which the atleast one antenna beam is applied to receive signals, the dedicatedresources being identified based on the at least one antenna beam andthe RACH preamble over RACH symbols in the determined RACH chunk overthe at least one antenna beam that is swept to receive signals.

In some embodiments, the RF transceiver 210 a-201 n is capable ofreceiving the RACH preamble including the beam ID using the RACH chunkfrom the RACH chunks mapped to at least one downlink signal symbolselected and the RACH preamble including the beam ID using an RACHpreamble sequence from the subset of RACH preamble sequences mapped toat least one downlink signal symbol selected.

The TX processing circuitry 215 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 225. The TX processing circuitry 215 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 210 a-210 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 215 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 205 a-205 n.

The controller/processor 225 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 225 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 210 a-210 n, the RX processing circuitry 220, andthe TX processing circuitry 215 in accordance with well-knownprinciples. The controller/processor 225 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 225 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 205 a-205 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 225.

The controller/processor 225 is also capable of executing programs andother processes resident in the memory 230, such as an OS. Thecontroller/processor 225 can move data into or out of the memory 230 asrequired by an executing process.

The controller/processor 225 is also coupled to the backhaul or networkinterface 235. The backhaul or network interface 235 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 235 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 235 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 235 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 235 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

In some embodiments, the controller/processor 225 is capable ofdetermining random access channel (RACH) configuration informationincluding RACH chunk and mapping, based on the RACH configurationinformation, downlink signal symbols to RACH chunks, the downlink signalsymbols transmitted on at least one of synchronization signal (SS), abroadcasting signal on a physical broadcasting channel (PBCH), or a beamreference signal (BRS).

In some embodiments, the controller/processor 225 is capable of mapping,based on the RACH configuration information, downlink signal symbols toa subset of RACH preamble sequences, the downlink signal symbols beingconveyed by at least one of synchronization signal (SS), a broadcastingsignal on a physical broadcasting channel (PBCH), or a beam referencesignal (BRS).

The memory 230 is coupled to the controller/processor 225. Part of thememory 230 could include a RAM, and another part of the memory 230 couldinclude a Flash memory or other ROM.

Although FIG. 2 illustrates one example of eNB 102, various changes maybe made to FIG. 2. For example, the eNB 102 could include any number ofeach component shown in FIG. 2. As a particular example, an access pointcould include a number of interfaces 235, and the controller/processor225 could support routing functions to route data between differentnetwork addresses. As another particular example, while shown asincluding a single instance of TX processing circuitry 215 and a singleinstance of RX processing circuitry 220, the eNB 102 could includemultiple instances of each (such as one per RF transceiver). Also,various components in FIG. 2 could be combined, further subdivided, oromitted and additional components could be added according to particularneeds.

FIG. 3 illustrates an example UE 116 according to embodiments of thepresent disclosure. The embodiment of the UE 116 illustrated in FIG. 3is for illustration only, and the UEs 111-115 of FIG. 1 could have thesame or similar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 3, the UE 116 includes an antenna 305, a radiofrequency (RF) transceiver 310, TX processing circuitry 315, amicrophone 320, and receive (RX) processing circuitry 325. The UE 116also includes a speaker 330, a processor 340, an input/output (I/O)interface (IF) 345, a touchscreen 350, a display 355, and a memory 360.The memory 360 includes an operating system (OS) 361 and one or moreapplications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

In some embodiments, the RF transceiver 310 is capable of receiving,from a base station (BS), random access channel (RACH) configurationinformation including RACH chunk information corresponding to at leastone antenna beam including a beam identifier (ID), transmitting, to theBS, an RACH preamble on the determined RACH chunk according to the RACHconfiguration information associated with the beam ID, and receiving,from the BS, an RACH response (RAR) corresponding to the transmittedRACH preamble, a random access-radio network temporary identification(RA-RNTI) of a downlink channel for an RAR transmission being calculatedbased on an index of a slot and an index of the RACH chunk on which theRACH preamble is transmitted.

In some embodiments, the RF transceiver 310 is capable of transmittingthe RACH preamble on dedicated resources over which the at least oneantenna beam is applied to receive signals, the RACH preamble over RACHsymbols in the determined RACH chunk over the at least one antenna beamthat is swept to receive signals, the RACH preamble including the beamID using the RACH chunk from the RACH chunks mapped to at least onedownlink signal symbol selected, and the RACH preamble including thebeam ID using an RACH preamble sequence from the subset of RACH preamblesequences mapped to at least one downlink signal symbol selected.

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS 361 stored in the memory 360 in order tocontrol the overall operation of the UE 116. For example, the processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as processes for CSI reportingon PUCCH. The processor 340 can move data into or out of the memory 360as required by an executing process. In some embodiments, the processor340 is configured to execute the applications 362 based on the OS 361 orin response to signals received from eNBs or an operator. The processor340 is also coupled to the I/O interface 345, which provides the UE 116with the ability to connect to other devices, such as laptop computersand handheld computers. The I/O interface 345 is the communication pathbetween these accessories and the processor 340.

The processor 340 is also coupled to the touchscreen 350 and the display355. The operator of the UE 116 can use the touchscreen 350 to enterdata into the UE 116. The display 355 may be a liquid crystal display,light emitting diode display, or other display capable of rendering textand/or at least limited graphics, such as from web sites.

In some embodiments, the processor 340 is capable of determining an RACHchunk based on the RACH configuration information received from the BS,re-selecting other RACH chunks each of which includes RACH symbols basedon the RACH chunk information, and performing a power ramping thatadjusts a transmit power of the RACH preamble. In such embodiments, theRACH configuration information comprises at least one of the index ofthe slot, the index of the RACH chunk, partitioning information, beamsweeping information, a preamble type, or retransmission information.

In some embodiments, the processor 340 is capable of identifyingdedicated resources for the BS to apply the at least one antenna beam,mapping, based on the RACH configuration information, downlink signalsymbols to RACH chunks, the downlink signal symbols transmitted on atleast one of synchronization signal (SS), a broadcasting signal on aphysical broadcasting channel (PBCH), or a beam reference signal (BRS).

In some embodiments, the processor 340 is capable of mapping, based onthe RACH configuration information, downlink signal symbols to a subsetof RACH preamble sequences, the downlink signal symbols being conveyedby at least one of synchronization signal (SS), a broadcasting signal ona physical broadcasting channel (PBCH), or a beam reference signal(BRS).

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

Although FIG. 3 illustrates one example of UE 116, various changes maybe made to FIG. 3. For example, various components in FIG. 3 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, theprocessor 340 could be divided into multiple processors, such as one ormore central processing units (CPUs) and one or more graphics processingunits (GPUs). Also, while FIG. 3 illustrates the UE 116 configured as amobile telephone or smartphone, UEs could be configured to operate asother types of mobile or stationary devices.

FIG. 4A is a high-level diagram of transmit path circuitry. For example,the transmit path circuitry may be used for an orthogonal frequencydivision multiple access (OFDMA) communication. FIG. 4B is a high-leveldiagram of receive path circuitry. For example, the receive pathcircuitry may be used for an orthogonal frequency division multipleaccess (OFDMA) communication. In FIGS. 4A and 4B, for downlinkcommunication, the transmit path circuitry may be implemented in a basestation (eNB) 102 or a relay station, and the receive path circuitry maybe implemented in a user equipment (e.g. user equipment 116 of FIG. 1).In other examples, for uplink communication, the receive path circuitry450 may be implemented in a base station (e.g. eNB 102 of FIG. 1) or arelay station, and the transmit path circuitry may be implemented in auser equipment (e.g. user equipment 116 of FIG. 1).

Transmit path circuitry comprises channel coding and modulation block405, serial-to-parallel (S-to-P) block 410, Size N Inverse Fast FourierTransform (IFFT) block 415, parallel-to-serial (P-to-S) block 420, addcyclic prefix block 425, and up-converter (UC) 430. Receive pathcircuitry 450 comprises down-converter (DC) 455, remove cyclic prefixblock 460, serial-to-parallel (S-to-P) block 465, Size N Fast FourierTransform (FFT) block 470, parallel-to-serial (P-to-S) block 475, andchannel decoding and demodulation block 480.

At least some of the components in FIGS. 4A 400 and 4B 450 may beimplemented in software, while other components may be implemented byconfigurable hardware or a mixture of software and configurablehardware. In particular, it is noted that the FFT blocks and the IFFTblocks described in this disclosure document may be implemented asconfigurable software algorithms, where the value of Size N may bemodified according to the implementation.

Furthermore, although this disclosure is directed to an embodiment thatimplements the Fast Fourier Transform and the Inverse Fast FourierTransform, this is by way of illustration only and may not be construedto limit the scope of the disclosure. It may be appreciated that in analternate embodiment of the present disclosure, the Fast FourierTransform functions and the Inverse Fast Fourier Transform functions mayeasily be replaced by discrete Fourier transform (DFT) functions andinverse discrete Fourier transform (IDFT) functions, respectively. Itmay be appreciated that for DFT and IDFT functions, the value of the Nvariable may be any integer number (i.e., 1, 4, 3, 4, etc.), while forFFT and IFFT functions, the value of the N variable may be any integernumber that is a power of two (i.e., 1, 2, 4, 8, 16, etc.).

In transmit path circuitry 400, channel coding and modulation block 405receives a set of information bits, applies coding (e.g., LDPC coding)and modulates (e.g., quadrature phase shift keying (QPSK) or quadratureamplitude modulation (QAM)) the input bits to produce a sequence offrequency-domain modulation symbols. Serial-to-parallel block 410converts (i.e., de-multiplexes) the serial modulated symbols to paralleldata to produce N parallel symbol streams where N is the IFFT/FFT sizeused in BS 102 and UE 116. Size N IFFT block 415 then performs an IFFToperation on the N parallel symbol streams to produce time-domain outputsignals. Parallel-to-serial block 420 converts (i.e., multiplexes) theparallel time-domain output symbols from Size N IFFT block 415 toproduce a serial time-domain signal. Add cyclic prefix block 425 theninserts a cyclic prefix to the time-domain signal. Finally, up-converter430 modulates (i.e., up-converts) the output of add cyclic prefix block425 to RF frequency for transmission via a wireless channel. The signalmay also be filtered at baseband before conversion to RF frequency.

The transmitted RF signal arrives at UE 116 after passing through thewireless channel, and reverse operations to those at eNB 102 areperformed. Down-converter 455 down-converts the received signal tobaseband frequency, and remove cyclic prefix block 460 removes thecyclic prefix to produce the serial time-domain baseband signal.Serial-to-parallel block 465 converts the time-domain baseband signal toparallel time-domain signals. Size N FFT block 470 then performs an FFTalgorithm to produce N parallel frequency-domain signals.Parallel-to-serial block 475 converts the parallel frequency-domainsignals to a sequence of modulated data symbols. Channel decoding anddemodulation block 480 demodulates and then decodes the modulatedsymbols to recover the original input data stream.

Each of eNBs 101-103 may implement a transmit path that is analogous totransmitting in the downlink to user equipment 111-116 and may implementa receive path that is analogous to receiving in the uplink from userequipment 111-116. Similarly, each one of user equipment 111-116 mayimplement a transmit path corresponding to the architecture fortransmitting in the uplink to eNBs 101-103 and may implement a receivepath corresponding to the architecture for receiving in the downlinkfrom eNBs 101-103.

5G communication system use cases have been identified and described.Those use cases can be roughly categorized into three different groups.In one example, enhanced mobile broadband (eMBB) is determined to dowith high bits/sec requirement, with less stringent latency andreliability requirements. In another example, ultra reliable and lowlatency (URLL) is determined with less stringent bits/sec requirement.In yet another example, massive machine type communication (mMTC) isdetermined that a number of devices can be as many as 100,000 to 1million per km2, but the reliability/throughput/latency requirementcould be less stringent. This scenario may also involve power efficiencyrequirement as well, in that the battery consumption should be minimizedas possible.

In LTE technologies, a time interval X which can contain one or more ofthe DL transmission part, guard, UL transmission part, and a combinationof thereof regardless of they are indicated dynamically and/orsemi-statically. Furthermore, in one example, the DL transmission partof time interval X contains downlink control information and/or downlinkdata transmissions and/or reference signals. In another example, the ULtransmission part of time interval X contains uplink control informationand/or uplink data transmissions and/or reference signals. In addition,the usage of DL and UL does not preclude other deployment scenariose.g., sidelink, backhaul, relay). In some embodiments of the currentdisclosure, “a subframe” is another name to refer to “a time intervalX,” or vice versa. In order for the 5G network to support these diverseservices are called network slicing.

In some embodiments, “a subframe” and “a time slot” can be usedinterchangeably. In some embodiments, “a subframe” refers to a transmittime interval (TTI), which may comprise an aggregation of “time slots”for UE″s data transmission/reception.

FIG. 5 illustrates a network slicing 500 according to embodiments of thepresent disclosure. An embodiment of the network slicing 500 shown inFIG. 5 is for illustration only. One or more of the componentsillustrated in FIG. 5 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 5, the network slicing 500 comprises an operator'snetwork 510, a plurality of RANS 520, a plurality of eNBs 530 a, 530 b,a plurality of small cell base stations 535 a, 535 b, a URLL slice 540a, a smart watch 545 a, a car 545 b, a, truck 545 c, a smart glasses 545d, a power 555 a, a temperature 555 b, an mMTC slice 550 a, an eMBBslice 560 a, a smart phone (e.g., cell phones) 565 a, a laptop 565 b,and a tablet 565 c (e.g., tablet PCs).

The operator's network 510 includes a number of radio access network(s)520—RAN(s)—that are associated with network devices, e.g., eNBs 530 aand 530 b, small cell base stations (femto/pico eNBs or Wi-Fi accesspoints) 535 a and 535 b, etc. The operator's network 510 can supportvarious services relying on the slice concept. In one example, fourslices, 540 a, 550 a, 550 b and 560 a, are supported by the network. TheURLL slice 540 a to serve UEs requiring URLL services, e.g., cars 545 b,trucks 545 c, smart watches 545 a, smart glasses 545 d, etc. Two mMTCslices 550 a and 550 b serve UEs requiring mMTC services such as powermeters and temperature control (e.g., 555 b), and one eMBB slice 560 arequiring eMBB serves such as cells phones 565 a, laptops 565 b, tablets565 c.

In short, network slicing is a method to cope with various differentqualities of services (QoS) in the network level. For supporting thesevarious QoS efficiently, slice-specific PHY optimization may also benecessary. Devices 545 a/b/c/d, 555 a/b are 565 a/b/c examples of userequipment (UE) of different types. The different types of user equipment(UE) shown in FIG. 5 are not necessarily associated with particulartypes of slices. For example, the cell phone 565 a, the laptop 565 b andthe tablet 565 c are associated with the eMBB slice 560 a, but this isjust for illustration and these devices can be associated with any typesof slices.

In some embodiments, one device is configured with more than one slice.In one embodiment, the UE, (e.g., 565 a/b/c) is associated with twoslices, the URLL slice 540 a and the eMBB slice 560 a. This can beuseful for supporting online gaming application, in which graphicalinformation are transmitted through the eMBB slice 560 a, and userinteraction related information are exchanged through the URLL slice 540a.

In the current LTE standard, no slice-level PHY is available, and mostof the PHY functions are utilized slice-agnostic. A UE is typicallyconfigured with a single set of PHY parameters (including transmit timeinterval (TTI) length, OFDM symbol length, subcarrier spacing, etc.),which is likely to prevent the network from (1) fast adapting todynamically changing QoS; and (2) supporting various QoS simultaneously.

In some embodiments, corresponding PHY designs to cope with differentQoS with network slicing concept are disclosed. It is noted that “slice”is a terminology introduced just for convenience to refer to a logicalentity that is associated with common features, for example, numerology,an upper-layer (including medium access control/radio resource control(MAC/RRC)), and shared UL/DL time-frequency resources. Alternative namesfor “slice” include virtual cells, hyper cells, cells, etc.

FIG. 6 illustrates an example number of digital chains 600 according toembodiments of the present disclosure. An embodiment of the number ofdigital chains 600 shown in FIG. 6 is for illustration only. One or moreof the components illustrated in FIG. 6 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

LTE specification supports up to 32 channel state information-referencesignal (CSI-RS) antenna ports which enable an eNB to be equipped with alarge number of antenna elements (such as 64 or 128). In this case, aplurality of antenna elements is mapped onto one CSI-RS port. For nextgeneration cellular systems such as 5G, the maximum number of CSI-RSports can either remain the same or increase.

For mmWave bands, although the number of antenna elements can be largerfor a given form factor, the number of CSI-RS ports—which can correspondto the number of digitally precoded ports—tends to be limited due tohardware constraints (such as the feasibility to install a large numberof ADCs/DACs at mmWave frequencies) as illustrated in FIG. 6. In thiscase, one CSI-RS port is mapped onto a large number of antenna elementswhich can be controlled by a bank of analog phase shifters 601. OneCSI-RS port can then correspond to one sub-array which produces a narrowanalog beam through analog beamforming 605. This analog beam can beconfigured to sweep across a wider range of angles 620 by varying thephase shifter bank across symbols or subframes. The number of sub-arrays(equal to the number of RF chains) is the same as the number of CSI-RSports N_(CSI-PORT). A digital beamforming unit 610 performs a linearcombination across N_(CSI-PORT) analog beams to further increaseprecoding gain. While analog beams are wideband (hence notfrequency-selective), digital precoding can be varied across frequencysub-bands or resource blocks.

FIG. 7 illustrates an example random access procedure 700 according toembodiments of the present disclosure. An embodiment of the randomaccess procedure 700 shown in FIG. 7 is for illustration only. One ormore of the components illustrated in FIG. 7 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

Before a UE can receive or transmit data to a gNB, the UE first needs todo the uplink random access procedure: to establish uplinksynchronization between UE and gNB, such as timing advance; and toobtain the resource for RRC connection request.

In LTE specification, contention based random access procedure consistsof four steps: a UE selects one of N RACH preamble sequences. UE selectsone RACH time-slot based on the RACH configuration to transmit thepreamble sequence. If UE does not receive RACH response from the gNBwith some timer, UE increases the transmit power with a configured stepsize and re-send the RACH preamble; a gNB sends random access response(RAR) to UE for one detected preamble sequence. The RAR message conveysthe information of a temporary C-RNTI, a timing advance value and anuplink resource grant for 3; after receiving the RAR, the UE sends msg3RRC connection request message to gNB; and a gNB sends msg4 in responseto the received msg3.

To cover different cell size, few preamble formats with different lengthof cyclic prefix (CP) and sequence are defined, as shown in TABLE 1.

TABLE 1 Preamble Formats Preamble Length of CP Length of sequence Guardtime Format (ms) (ms) (ms) 0 0.103 0.8 0.097 1 0.684 0.8 0.516 2 0.2031.6 0.197 3 0.684 1.6 0.716 4 0.015 0.133

The random access design for new communication system such 5G has a fewnew challenges. In one example, a gNB needs to use multiple receivebeams to cover the whole cell area in the uplink. In the design of RACH,the multi-beam based operation of the gNB may be considered for thecoverage of RACH. In another example, the gNB may or may not have beamreciprocity between Tx and Rx beams. The design of random access mayconsider both cases. When the gNB does not have beam reciprocity, the UEis not able to identify the best gNB Rx beam for random access based onthe downlink initial access signal the UE can measure; special design isneeded to ensure the preamble sent from the UE is detected by the gNBsuccessfully.

In yet another example, the UE may also have different level of beamreciprocity between UE's Tx and Rx beams. If UE has beam reciprocity,the UE is able to figure out which is the best beam for sending randomaccess based on the downlink initial access signal measurement. However,if UE has no beam reciprocity, the UE may not be able to figure out thebest transmit beam. In the design of random access, one needs toconsider the beam reciprocity capability of UEs.

In some embodiments, the delay of random access, if the number of beamsis large, the delay of random access may be large due to the multi-beamoperation. How to minimize the random access delay is an importantconsideration in the design.

In some embodiments, one random access occasion consists of one or moreRACH chunks and each RACH chunk consists of one or more RACH symbols.The number of RACH chunks in one random access occasion is Q>=1 and thenumber of RACH symbol in each RACH chunk is P>=1.

Once the random access preamble is transmitted and regardless of thepossible occurrence of a measurement gap or a sidelink discovery gap fortransmission or a sidelink discovery gap for reception, the MAC entitymay monitor the PDCCH of the SpCell for sandom access sesponse(s) (RARs)identified by the RA-RNTI defined below, in the RA Response window whichstarts at the subframe that contains the end of the preambletransmission plus three subframes and has length ra-ResponseWindowSize.If the UE is a BL UE or a UE in enhanced coverage, RA Response windowstarts at the subframe that contains the end of the last preamblerepetition plus three subframes and has length ra-ResponseWindowSize forthe corresponding coverage level.

If the UE is an NB-IoT UE, in case the number of NPRACH repetitions isgreater than or equal to 64, the RA Response window starts at thesubframe that contains the end of the last preamble repetition plus 41subframes and has length ra-ResponseWindowSize for the correspondingcoverage level, and in case the number of NPRACH repetitions is lessthan 64, the RA Response window starts at the subframe that contains theend of the last preamble repetition plus 4 subframes and has lengthra-ResponseWindowSize for the corresponding coverage level. The RA-RNTIassociated with the PRACH in which the Random Access Preamble istransmitted, is computed as: RA-RNTI=1+t_id+10*f_id where t_id is theindex of the first subframe of the specified PRACH (0≤t_id<10), and f_idis the index of the specified PRACH within that subframe, in ascendingorder of frequency domain (0≤f_id<6) except for NB-IoT UEs, BL UEs orUEs in enhanced coverage. If the PRACH resource is on a TDD carrier, thef_id is set to ƒ_(RA), where ƒ_(RA) is defined in LTE specification.

For BL UEs and UEs in enhanced coverage, RA-RNTI associated with thePRACH in which the random access preamble is transmitted, is computed asRA-RNTI=1+t_id+10*f_id+60*(SFN_id mod (Wmax/10)) where t_id is the indexof the first subframe of the specified PRACH (0≤t_id<10), f_id is theindex of the specified PRACH within that subframe, in ascending order offrequency domain (0≤f_id<6), SFN_id is the index of the first radioframe of the specified PRACH, and Wmax is 400, maximum possible RARwindow size in subframes for BL UEs or UEs in enhanced coverage. If thePRACH resource is on a TDD carrier, the f_id is set to ƒ_(RA), whereƒ_(RA) is defined in LTE specification.

For NB-IoT UEs, the RA-RNTI associated with the PRACH in which theRandom Access Preamble is transmitted, is computed as RA-RNTI=1+SFN_id/4where SFN_id is the index of the first radio frame of the specifiedPRACH.

In the present disclosure, the term of Tx/Rx beam correspondence isdefined as follows.

In one example, Tx/Rx beam correspondence at TRP holds if at least oneof the following is satisfied: TRP is able to determine a TRP Rx beamfor the uplink reception based on UE's downlink measurement on TRP's oneor more Tx beams; or TRP is able to determine a TRP Tx beam for thedownlink transmission based on TRP's uplink measurement on TRP's one ormore Rx beams. In another example, Tx/Rx beam correspondence at UE holdsif at least one of the following is satisfied: a UE is able to determinea UE Tx beam for the uplink transmission based on UE's downlinkmeasurement on UE's one or more Rx beams; or a UE is able to determine aUE Rx beam for the downlink reception based on TRP's indication based onuplink measurement on UE's one or more Tx beams.

In the present disclosure, the two terminologies, “RACH symbol” and“RACH resource” are used interchangeably. In the present disclosure, thetwo terminologies, “slot” and “subframe” are used interchangeably, whichmean a number of consecutive OFDM symbols, e.g., 7 or 14 consecutiveOFDM symbols. A RACH transmission occasion can include one or more RACHsymbols/resources selected from one or more RACH chunks. One RACH chunkcan be referred to as a subset of RACH resources. In some embodiments,the two terminologies, “RACH occasion,” “PRACH duration” and “PRACH” areused interchangeably.

In some embodiment, a UE is configured to apply a same UE Tx beam on theselected RACH resources belonging to a same RACH chunk. In anotherembodiment, a UE is allowed to apply different UE Tx beams on theselected RACH resources across different RACH chunks. In yet anotherembodiment, one random access occasion (or a PRACH duration) consists ofone or more RACH chunks and each RACH chunk consists of one or more RACHsymbols. In such embodiment, a PRACH duration is an integer number of(consecutive) time slots. The number of RACH chunks in one random accessoccasion is Q>=1 and the number of RACH symbol in each RACH chunk isP>=1.

FIG. 8A illustrates an example RACH occasion 810 according toembodiments of the present disclosure. An embodiment of the RACHoccasion 810 shown in FIG. 8A is for illustration only. One or more ofthe components illustrated in FIG. 8A can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In one example, the RACH symbols in one RACH chunk are contiguous. Anexample is shown FIG. 8A. As illustrated in FIG. 8A, one RACH occasion800 has Q=4 RACH chunks. Each RACH chunk has P contiguous RACH symbols.RACH chunk #1 801 has contiguous RACH symbols, RACH symbol #1 811, RACHsymbol #2 812 and to RACH symbol #P 813. RACH chunk #2 802 hascontiguous RACH symbols, RACH symbol #1 814, RACH symbol #2 815, and toRACH symbol #P 816.

FIG. 8B illustrates another example RACH occasion 830 according toembodiments of the present disclosure. An embodiment of the RACHoccasion 830 shown in FIG. 8B is for illustration only. One or more ofthe components illustrated in FIG. 8B can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In one example, the RACH symbols in one RACH chunk arescattered/distributed. An example is shown in FIG. 8B. As illustrated inFIG. 8B, one RACH occasion 800 has Q=4 RACH chunks. Each RACH chunk hasP scattered RACH symbols. RACH chunk #1 801 has scattered RACH symbols,RACH symbol #1 811, RACH symbol #2 812 and to RACH symbol #P 813. RACHchunk #2 802 has scattered RACH symbols, RACH symbol #1 814, RACH symbol#2 815, and to RACH symbol #P 816.

In some embodiments, the gNB utilizes the same receive beam on all theRACH symbols belonging to the same RACH chunk and the gNB could utilizedifferent receive beams on different RACH chunks. In one embodiment, thegNB could sweep Rx beams over the RACH symbols within one RACH chunk.

In some embodiments, the UE is configured to use the same UE Tx beamover the RACH symbols within one RACH chunk. In one method, the UE isconfigured to use different UE Tx beams on the RACH symbols within oneRACH chunk.

FIG. 8C illustrates example RACH symbols 870 according to embodiments ofthe present disclosure. An embodiment of the RACH symbols 870 shown inFIG. 8C is for illustration only. One or more of the componentsillustrated in FIG. 8C can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, one RACH symbols is comprised by a cyclic prefixpart and preamble sequence part, as illustrated in FIG. 8C. One RACHsymbol 850 contains a cyclic prefix part 851 and a RACH preamble part852. The length of cyclic prefix part 851 may be long enough toaccommodate variation of round trip delay and propagation delay of allUEs in one cell.

In some embodiments, the UE is configured to select one RACH chunk forthe uplink preamble transmission based on the measurement of downlinkinitial access signal. For example, the UE is configured to pick theRACH chunk index based on the index of OFDM symbol where the UE measuresthe strongest RSRP of initial synchronization signals. For example, theUE is configured to pick the RACH chunk index based on the index of OFDMsymbol where the UE measures the strongest RSRP of beam referencesignal. For example, the UE is configured to pick the RACH chunk indexbased on the beam ID witch which the UE measures the strongest RSRP ofthe beams.

In some embodiments, the UE is configured to transmit the same preamblesequence in the RACH symbols in the one selected RACH chunks.

FIG. 9A illustrates an example RACH channel structure 900 according toembodiments of the present disclosure. An embodiment of the RACH channelstructure 900 shown in FIG. 9A is for illustration only. One or more ofthe components illustrated in FIG. 9A can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 9A, one RACH occasion has Q=6 RACH chunks and each RACHchunk has P=1 RACH symbols. The TRP has 6 receive beams and the TRPsweeps the receive beams over these 6 RACH symbols. The UE is configuredto transmit preamble on one of these RACH symbol. The configuration ofthis example is applicable to the scenario in which the TRP has beamreciprocity between Tx and Rx beams. The UE is capable to calculate thebest receive beam of TRP for uplink preamble and thus is capable to pickthe best RACH symbol.

FIG. 9B illustrates another example RACH channel structure 920 accordingto embodiments of the present disclosure. An embodiment of the RACHchannel structure 920 shown in FIG. 9B is for illustration only. One ormore of the components illustrated in FIG. 9B can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 9B, one RACH occasion has Q=3 RACH chunks and each RACHchunk has P=2 RACH symbols. The symbols in one RACH chunk arecontiguous. The TRP has 3 receive beams and the TRP sweeps the receivebeams over these 3 RACH symbols. The TRP utilizes Rx beam #0 on bothRACH symbols in RACH chunk #1; the TRP utilizes Rx beam #1 on both RACHsymbols in RACH chunk #2; and the TRP utilizes Rx beam #2 on both RACHsymbols in RACH chunk #3. The UE is configured to transmit preamble onone of these RACH chunk and repeat the same preamble sequence of twoRACH symbols in the selected RACH chunk. The configuration as shown inFIG. 9B allows the UE to use Tx beam sweeping method to transmit uplinkpreamble sequence. That is applicable to the scenario in which the UEdoes not have beam reciprocity between Tx and Rx beams. The UE iscapable to sweep Tx beams on preamble sequence to improve the uplinkreliability.

FIG. 9C illustrates yet another example RACH channel structure 940according to embodiments of the present disclosure. An embodiment of theRACH channel structure 940 shown in FIG. 9C is for illustration only.One or more of the components illustrated in FIG. 9C can be implementedin specialized circuitry configured to perform the noted functions orone or more of the components can be implemented by one or moreprocessors executing instructions to perform the noted functions. Otherembodiments are used without departing from the scope of the presentdisclosure.

An example of RACH channel configuration with scattered symbols is shownin FIG. 9C. As shown in FIG. 9C, one RACH occasion has Q=3 RACH chunksand each RACH chunk has P=2 RACH symbols. The symbols in one RACH chunkare scattered. Similar to the aforementioned embodiments, one UE isconfigured to transmit the same preamble sequence in two RACH symbolswith different Tx beams. The scattered RACH symbols give more channeldiversity to improve the reliability of uplink preamble transmission.

In some embodiments, one RACH occasion could occupy one or more uplinksubframes. In such embodiments, the RACH occasion is periodic. In someembodiments, the UE can be configured to select RACH symbols forpreamble transmission, according to one of the following methods. In oneexample, randomly select one RACH symbol in a selected RACH chunk. Therandom function may be such that each of the RACH symbols in theselected RACH chunk can be chosen with equal probability. In anotherexample, select all the RACH symbols in a selected subset of RACH chunksin a PRACH duration. The size of the selected subset can be 1, 2, . . ., which can be configured via broadcast signaling or pre-configured(i.e., fixed in the specification). Which method for the UE to use canbe configured via broadcast signaling, or pre-configured (i.e., fixed inthe specification).

In some embodiment, one RACH occasion could occupy one or more uplinksubframes. The RACH occasion is periodic. In some embodiment, the UE isconfigured to receive the RACH configuration from system informationmessage, for example, MIB and SIB.

In some embodiment, the RACH configuration comprises one or more ofcomponents. In one example, the RACH configuration comprises a preambleformat that defines the format of one RACH symbol. In one example, onepreamble format defines the length of cyclic prefix and the length ofRACH symbol. In another example, the RACH configuration comprises apreamble type that defines if a Tx beam ID is conveyed in the preamblesequence or not. In one example, if the preamble type is 0, the preamblesequence does not convey the information of Tx beam ID and if thepreamble type is 1, the preamble sequence coveys the information of Txbeam ID. If a UE is configured with preamble type 1, the preamblesequences are divided into M exclusive groups and each preamble groupcorresponds to a TRP Tx beam ID. The UE is configured to select frompreamble sequence from the group that is mapped to the TRP Tx beam theUE selects.

In yet another example, the RACH configuration comprise a number of RACHChunk in one RACH occasion, Q>=1. In another example, the RACHconfiguration comprises a number of RACH symbol in one RACH chunk, P>=1.In another example, the RACH configuration comprises a type of RACHchunk: the RACH chunk could have two methods of the RACH symbols. Onemethod is the RACH symbols are contiguous in one RACH chunk, as shown inFIG. 8A. Another method is that RACH symbols are scattered as shown inFIG. 8B.

In yet another example, following preamble transmission method is usedto indicate a UE. In one instance, the UE transmits a same preamblesequence on all the RACH symbols in a selected RACH chunk. In anotherinstance, the UE transmits a same preamble sequence on a randomlyselected RACH symbol in a selected RACH chunk. In yet another instance,the UE transmits different (random) preamble sequences on the selectedRACH symbols in a selected RACH chunk.

In yet another example, following UE Tx beam sweeping is used toindicate a UE. In one instance, the UE can use the same Tx beam ondifferent RACH symbols (or RACH resources) in one RACH chunk. In anotherinstance, the UE can use different Tx beams on different RACH symbols(or RACH resources) in one RACH chunk.

In yet another example, the RACH configuration comprises a method ofselecting RACH chunk for preamble retransmission: one RACH occasioncould have multiple RACH chunk and the TRP could apply different uplinkRx beams over those RACH chunks. If the TRP does not have reciprocitybetween Tx and Rx beams, the UE may be not able to figure out which Rxbeam (i.e., RACH chunk) is the best for preamble transmission. So if apreamble transmission is failed, the UE could be configured to re-selectthe RACH chunk for the preamble re-transmission. Multiple modes could bedefined. In one example, one mode is that the UE is configured to usethe same RACH chunk. In one example, the UE is configured to select thenext RACH chunk index based on the previous RACH chunk index byfollowing some equation. In one example, the UE is configured to selectthe RACH chunk index based on a pseudorandom sequence. The pseudorandomsequence could be generated from the initialization based on theidentity of the UE.

In yet another example of time and frequency resource configuration, thesubframe configuration of RACH occasions comprises the indices ofsubframe where RACH occasions/durations are mapped and the periodicityof RACH occasions.

In yet another example of the RAR type, there could be type of methodsto transmit RAR. In one instance, one Tx beam is transmitted. In anotherinstance, RAR is transmitted through a Tx beam sweeping. In suchexample, if the RAR type is 0, the RAR is sent as a PDSCH indicated by aDCI with RA-RNTI. In such example, RA-RNTI can be a function of RACHchunk index. RA-RNTI can be function of RACH chunk index and RACH symbolindex within one RACH chunk (e.g., two RA-RNTI calculation scheme). Insuch example, if the RAR type is 1, the RAR is sent through Tx beamsweeping and the configuration of RAR occasion is conveyed in systeminformation channel.

In some embodiments, the UE is configured to determine a method oftransmitting RACH preamble based on UE's capability. In one example, ifthe UE is with beam correspondence, the UE chooses the methodtransmitting RACH preamble on a randomly selected RACH symbol within aselected RACH chunk. In another example, if the UE is without beamcorrespondence, the UE chooses the method of transmitting PRACH preambleon all the RACH symbols in a selected RACH chunk. The UE can be furtherconfigured with two sets of RACH chunks in a PRACH duration, forexample, a first set to be used by the UE with beam correspondence toselect one RACH resource in a RACH chunk and a second set to be used bythe UE without beam correspondence to select all the RACH resources in aRACH chunk.

In yet another example, the RACH configuration comprises the subframeconfiguration of RACH occasions comprising the information indices ofsubframe where RACH occasions are mapped and the periodicity of RACHoccasions. In yet another example, the RACH configuration comprises theRAR type: there could be type of methods to transmit RAR. One method isto transmit with one Tx beam. Another method is to transmit RAR througha Tx beam sweeping. In one example, if the RAR type is 0, the RAR issent as a PDSCH indicated by a DCI with RA-RNTI. If the RAR type is 1,the RAR is sent through Tx beam sweeping and the configuration of RARoccasion is conveyed in system information channel.

In some embodiments, the RACH configuration could be configured by RACHconfiguration index and the RACH configuration index is signaled insystem information channel, e.g., MIB (PBCH) and/or SIB (PBCH2). The UEis configured to calculate the RACH configuration information, forexample, the detailed information listed above, based on the receivedRACH configuration index. One example of the RACH configuration index isshown in TABLE 2A and 2B.

TABLE 2A RACH configuration index Method of selecting RACH Number ofRACH config- Number of RACH chunk for uration Preamble Preamble RACHsymbols per re-trans- index format type chunk (Q) Chunk (P) mission 0 00 7 1 0 1 0 0 7 4 0 2 0 1 7 1 1 3 0 1 7 4 1 4 0 0 7 4 1 5 0 0 7 4 2 6 10 7 1 0 7 1 0 7 1 0

TABLE 2B RACH configuration index Preamble UE Tx beam RACH Time andfrequency Transmit sweeping Chunk RAR resource index method method Typetype Index of slots 1 0 0 0 Index of slots 1 0 0 0 Index of slots 1 0 00 Index of slots 2 0 0 0 Index of slots 2 1 1 1 Index of slots 2 1 1 1Index of slots 2 0 0 1 Index of slots 2 1 1 1

As shown in TABLE 2A and 2B, one example of RACH configuration index 0defines: preamble format is 0; preamble type is 0, i.e., the preamblesequence does not convey Tx beam ID; each RACH occasion has Q=7 RACHchunk and each RACH chunk has P=1 RACH symbol; and the RACH symbols arecontiguous in each RACH chunk.

As shown in TABLE 2A and 2B, one example of RACH configuration index 3defines: preamble format is 0; preamble type is 1. The preamble sequencemay convey one Tx beam ID; each RACH occasion has Q=7 RACH chunks andeach RACH chunk has P=4 RACH symbols; and the RACH symbols arecontiguous in each RACH chunk.

In some embodiments, the gNB can indicate more than one, e.g., RACHconfiguration indices and the UE is configured to select one of thoseconfigured RACH configuration indices for the RACH procedure.

In one embodiment, a gNB configures two RACH configurations. In a firstRACH configuration according to a first RACH configuration index, eachRACH chunk has P=1 RACH symbols. In a second RACH configurationaccording to a second RACH configuration index, each RACH chunk has P>1RACH symbols. The UE is configured to select one of those two RACHconfigurations based on UE's beam correspondence capability. The UE withTx/Rx beam correspondence can choose the first RACH configuration andthe UE without Tx/Rx beam correspondence or with partial Tx/Rx beamcorrespondence can choose the second RACH configuration.

In one embodiment, two different RACH configuration indices can beconfigured to the UE through system information. These two RACHconfiguration indices can configure different sets of RACH resources orRACH chunks. The UE is configured to choose from one of these twoconfigured RACH configurations and then transmit the RACH preamble onthe RACH resources configured based on the selected RACH configurationindex.

In one embodiment, one RACH configuration index is used to configure twoPRACHs or PRACH durations. An example is shown in TABLE 2C. The UE isconfigured to calculate the PRACH configuration(s) based on the RACHconfiguration index received in system information. As shown in TABLE2C, for each RACH configuration index, the information can includefollowing parameters. In one example, the information may include thenumber of PRACH configurations, N_(PRACH). In one example, theinformation may include the common parameters for all N_(PRACH) PRACHconfigurations: the information can include the information of slotindex for PRACH if the RACH resources of these two RACN configurationare overlapped in the same time and frequency resource; the informationcan include the PRACH preamble format and PRACH preamble type; and theinformation can include the number of RACH chunks and the number ofsymbols in one RACH chunk.

In one example, the information may include the unique parameters for afirst PRACH configuration: the information can include the RAR typeinformation for a first PRACH configuration, for example, the RA-RNTIcalculation method and RAR window configuration; the information caninclude the RACH preamble transmit method; and the information caninclude the UE Tx beam sweeping method.

In one example, the information may include the unique parameters for asecond PRACH configurations: the information can include the RAR typeinformation for a second RPACH configuration, for example, the RA-RNTIcalculation method and RAR window configuration; the information caninclude the RACH preamble transmit method; and the information caninclude the UE Tx beam sweeping method.

The UE is configured to calculate the configuration of each PRACHconfigured by the RACH configuration index based on the commonparameters and unique parameters.

TABLE 2C RACH configuration RACH Number of configuration PRACH Commonparameters for Parameters for a first Parameters for a second indexconfigurations all PRACH configurations PRACH configuration PRACHconfiguration . . . 0 1 Common configuration Parameters for a first — —for all 1 PRACH PRACH configuration. configurations: Parameters caninclude common configuration the preamble transmit can include slotindex method, RA-RNTI of PRACH, preamble calculation method, type,number of RACH RAR windowing, UE chunks and RACH Tx beam sweepingsymbols 1 2 Common configuration Parameters for a first Parameters for asecond — for all 2 PRACH PRACH configuration. PRACH configuration.configurations: Parameters can include Parameters can include commonconfiguration the preamble transmit the preamble transmit can includeslot index method, RA-RNTI method, RA-RNTI of PRACH, preamblecalculation method, calculation method, type, number of RACH RARwindowing, UE RAR windowing, UE chunks and RACH Tx beam sweeping Tx beamsweeping symbols . . . . . . . . . . . . . . . . . .

In some embodiments, the UE can be configured to do the following forthe PRACH retransmissions. In one example, the UE increases the Tx powerfor the preamble transmission by the step size Δ_(P). The can beconfigured by the gNB. In another example, RACH chunk selection: the UEcan keep the same the RACH chunk or select a different RACH chunk forthe preamble retransmission. In yet another example, the UE switch theUE Tx beam(s) used for RACH preamble transmission in the preambleretransmission.

In some embodiments, the UE can be configured with the one or more UEbehavior configurations that can include the Tx power ramping, RACHchunk selection/reselection and UE switching UE Tx beam, for preambleretransmission. The UE is configured to select one of thoseconfigurations based on the UE's beam correspondence capability.

In some embodiments, the UE can be configured to first use Tx powerramping and then RACH chunk selection in case of preambleretransmission. In one method, in case of preamble retransmission, theUE increases the Tx power for preamble 1^(st) transmission, 2^(nd)retransmission until n-th retransmission. If the preamble n-thretransmission still failed, the UE is configured to switch to anotherRACH chunk and use this new RACH chunk for the n+1-th retransmissionuntil 2n-th retransmission, during which the UE is configured toincrease the Tx power with Δ_(P) for every new retransmission.

In some embodiments, the UE can be configured to first use RACH chunkselection and then use Tx power ramping in case of preambleretransmission. In one method, in case of preamble retransmission, theUE reselects the RACH chunk for preamble 1^(st) transmission, 2^(nd)retransmission until n-th retransmission but with the same Tx power. Ifthe preamble n-th retransmission still failed, the UE is configured toincrease the Tx power by Δ_(P) and use a new Tx power for the n+1-thretransmission until 2n-th retransmission, during which the UE isconfigured to reselect the RACH chunk for every new retransmission.

In some embodiments, the UE can be configured to use RACH chunkselection and Tx power ramping simultaneously. In one method, the UEuses Tx power P_(Tx0) and RACH chunk i₀ for the initial preambletransmission. If no corresponding RAR is received, the UE transmit theRACH preamble with Tx power P_(Tx0)+Δ_(P) and a new RACH chunk i₁ basedon the RACH chunk reselection method configured by the gNB.

In some embodiments, the UE can be configured with one or more Tx beamswitching methods and the UE is configured to select the Tx beamswitching method based on its beamforming capability and beamcorrespondence capability. In one method, in the case of the UE has beamcorrespondence, the UE can choose not using Tx beam switching and the Txbeam used for preamble transmission can be the best beam learning basedon the measurement of DL initial access signals. In another method, inthe case of the UE without Tx beamforming capability, the UE can choosenot using Tx beam switching for the preamble retransmission.

In some embodiments, the UE is configured to select the preamblesequence based on the preamble type indicated by the RACH configuration.In one embodiment, the preamble type is indicated by a RACHconfiguration index that is signaled in system information message.

In some embodiments, assume the UE is configured with L availablepreamble sequence for random access. The UE is also configured withnumber of Tx beams used for DL initial access signals, N_(B). If the UEis configured with preamble type 0, the UE is configured to randomlyselect one sequence from those L preamble sequence. If the UE isconfigured with preamble type 1, the UE is configured to select thepreamble sequence through the following procedure. In step 1, the UEcalculates the best Tx beam ID that corresponds to the strongest RSRP ofDL initial signals. In one example, the initial synchronization signalsare transmitted over multiple OFDM symbol through Tx beam sweeping. Thebest Tx beam ID is the OFDM symbol index where the UE detects thestrongest RSRP of initial synchronization signals. In another example,the best Tx beam ID is the beam ID with the strongest RSRP measured frombeam reference signals.

In step 2, assume the Tx beam ID selected by the UE is nϵ[0, 1, . . . ,N_(B)−1]. In this step, in one embodiment, the UE to select the preamblesequence from preamble ID set [0, . . . , L−1] is given as follows. Inone example for the case of mod (L, N_(B))>0, if the Tx beam ID is nϵ[0,. . . , mod(L, N_(B))−1], the UE uniformly and randomly selects onepreamble sequence from sequence ID set:

$\left\lbrack {0,1,\ldots\mspace{11mu},\left\lfloor \frac{L}{N_{B}} \right\rfloor} \right\rbrack + {n \times {\left( {\left\lfloor \frac{L}{N_{B}} \right\rfloor + 1} \right).}}$If the Tx beam ID is nϵ[mod (L, N_(B)), . . . , N_(B)−1], the UEuniformly and randomly selects one preamble sequence from sequence IDset:

$\left\lbrack {0,1,\ldots\mspace{11mu},{\left\lfloor \frac{L}{N_{B}} \right\rfloor - 1}} \right\rbrack + {\left( {n - {{mod}\left( {L,N_{B}} \right)}} \right) \times \left( \left\lfloor \frac{L}{N_{B}} \right\rfloor \right)} + {\left\lfloor \frac{L}{N_{B}} \right\rfloor \times {\left( {{{mod}\left( {L,N_{B}} \right)} + 1} \right).}}$In another example for the case of mod (L, N_(B))==0, For the Tx beamID: nϵ[0, . . . , N_(B)−1], the UE uniformly and randomly selects onepreamble sequence from sequence ID set:

$\left\lbrack {0,1,\ldots\mspace{11mu},{\left\lfloor \frac{L}{N_{B}} \right\rfloor - 1}} \right\rbrack + {n \times {\left\lfloor \frac{L}{N_{B}} \right\rfloor.}}$In another embodiment, the UE to select the preamble sequence frompreamble ID set [0, . . . , L−1] is given as follows. In one example forthe Tx beam ID: nϵ[0, . . . , N_(B)−1], the UE selects one preamblesequence from preamble sequence IDs that satisfy the condition:l=n+N_(B)×i; with i=0, 1, 2, . . . , l≥0 and l≤L.

In one embodiment, the preamble ID set is [L₀, L₀+1, . . . , L₀+L−1],the preamble sequence ID the UE selects would be {tilde over(L)}=L₀+{circumflex over (L)}, where {circumflex over (L)} is thepreamble ID calculated using the aforementioned embodiments.

In some embodiments, the UE is configured to repeat the selectedpreamble sequence in multiple RACH symbols in one RACH chunk. In someembodiment, a UE is configured with a method of switching RACH chunk.The method defines the procedure on how the UE selects the RACH chunkfor the random access preamble sequence re-transmission when onepreamble sequence transmission is failed. In some embodiment, the methodof switching RACH chunk is signaled through RACH configuration index.

In some embodiments, the RACH resource index can be associated with theTRP Tx beam ID. The UE is configured to select the RACH resource indexfor preamble transmission based on the UE's determination of TRP Tx beamID.

In some embodiments, a UE is configured with a method of switching RACHchunk. The method defines the procedure on how the UE selects the RACHchunk for the random access preamble sequence re-transmission when onepreamble sequence transmission is failed. In some embodiments, themethod of switching RACH chunk is signaled through RACH configurationindex.

Assume there are totally Q>=1 RACH Chunks in one RACH occasion and theRACH chunk index is [0, 1, . . . , Q−1]. Assume the RACH chunk indexselected first transmission of preamble is q₀. In one embodiment, theindex of RACH chunk for first preamble retransmission is (q₀+1) (mod Q)and the index of RACH chunk for n-th preamble retransmission is (q₀+n)(mod Q). In another embodiment, the index of RACH chunk for firstpreamble retransmission is (q₀−1) (mod Q) and the index of RACH chunkfor n-th preamble retransmission is (q₀−n) (mod Q). In yet anotherembodiment, the index of RACH chunk for first preamble retransmission is(q₀−1) (mod Q) and the index of RACH chunk for second preambleretransmission is (q₀+1) (mod Q).

FIG. 10A illustrates an example RACH chunk 1000 according to embodimentsof the present disclosure. An embodiment of the RACH chunk 1000 shown inFIG. 10A is for illustration only. One or more of the componentsillustrated in FIG. 10A can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

The index of RACH chunk for n-th preamble retransmission is

${\left( {q_{0} + {\left( {- 1} \right)^{n}\left\lceil \frac{n - 1}{2} \right\rceil}} \right)\left( {{mod}Q} \right)},$for n=1, 2, . . . . An example for this method is shown in FIG. 10A. Asillustrated in FIG. 10A, here are Q=6 RACH chunks. The UE selects RACHchunk #2 1001 for the initial preamble transmission. Then the index ofRACH chunk for first retransmission is (2−1) (mod 6)=1, that is RACHchunk#1 1005. The index of RACH chunk for second retransmission is

${{\left( {2 + {\left( {- 1} \right)^{- 2}\left\lceil \frac{2 - 1}{2} \right\rceil}} \right)\left( {{mod}\; 6} \right)} = 3},$which is RACH chunk #3, 1002.

In one embodiment, the index of RACH chunk for first preambleretransmission is (q₀+1) (mod Q) and the index of RACH chunk for secondpreamble retransmission is (q₀−1) (mod Q). The index of RACH chunk forn-th preamble retransmission is

${\left( {q_{0} - {\left( {- 1} \right)^{n}\left\lceil \frac{n - 1}{2} \right\rceil}} \right)\left( {{mod}Q} \right)},$for n=1, 2, . . . .

FIG. 10B illustrates another example RACH chunk 1020 according toembodiments of the present disclosure. An embodiment of the RACH chunk1020 shown in FIG. 10B is for illustration only. One or more of thecomponents illustrated in FIG. 10B can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, the index of RACH chunk for first preambleretransmission is (q₀+1) (mod Q) and the index of RACH chunk for secondpreamble retransmission is (q₀−2) (mod Q). The index of RACH chunk forn-th preamble retransmission is (q₀−(−1)^(n)×n) (mod Q), for n=1, 2, . .. . An example for this method is shown in FIG. 10B. As illustrated inFIG. 10B, there are Q=6 RACH chunks. The UE selects RACH chunk #2 1001for the initial preamble transmission. Then the index of RACH chunk forfirst retransmission is (2+1) (mod 6)=3, that is RACH chunk#2 1001. Theindex of RACH chunk for second retransmission is (2−2) (mod 6)=0, whichis RACH chunk #0, 1003.

In one embodiment, the index of RACH chunk for first preambleretransmission is (q₀−1) (mod Q) and the index of RACH chunk for secondpreamble retransmission is (q₀+2) (mod Q). The index of RACH chunk forn-th preamble retransmission is (q₀+(−1)^(n)×n) (mod Q), for n=1, 2, . .. .

In some embodiments, the indices of RACH chunk for the firsttransmission and retransmissions {q₀, q₁, q₂,} are generated frompseudo-random sequence. The pseudo-random sequence is generated based oninitialization with UE's ID or the Tx beam ID of which the UE measuresthe strongest RSRP of SS and/or BRS.

In some embodiments, the indices of RACH chunk for the retransmission is{q₀+Δ₀, q₀+Δ₁, q₀+Δ₂, . . . }, where q₀ is the RACH chunk index the UEselects for the initial transmission of preamble and {Δ₀, Δ₁, Δ₂, . . .} are the offset the UE used to calculate the RACH chunk index forfirst, second, third, . . . , preamble retransmission. The {Δ₀, Δ₁, Δ₂,. . . } is generated from pseudo-random sequence. The pseudo-randomsequence is generated based on initialization with UE's ID or the Txbeam ID of which the UE measures the strongest RSRP of SS and/or BRS.

In some embodiments, a UE is configured with a method of transmittingRAR. The method of transmitting RAR can be configured through RACHconfiguration index.

In some embodiments, the RAR is sent in downlink allocation scheduled bythe downlink control channel, e.g., PDCCH. The UE is configured tomonitor the PDCCH for the RAR identified by the RA-RNTI.

In some embodiments, the RA-RNTI of PDCCH scheduling RAR transmission isassociated with the RACH chunk index and/or RACH symbol index. In oneexample, the RA-RNTI is calculated based on a RACH chunk index. Inanother example, RA-RNTI is calculated based on a RACH chunk index and aRACH symbol index. The UE can be configured which method to use forRA-RNTI calculation in PRACH configuration.

In some embodiments, the UE is configured to calculate the RA-RNTI formonitoring PDCCH scheduling RAR that is associated with one preambletransmission based on the method of transmitting this RACH preamble thisUE used. In one example, if the UE transmits RACH preamble on one RACHsymbol in a selected RACH chunk, then the UE monitors the PDCCH for RARbased on the RA-RNTI that is calculated based at least partly based onboth the index of RACH chunk and the index of RACH symbol where the RACHpreamble is transmitted. If the UE transmits repeated (or multiple) RACHpreamble on all the RACH symbols in a selected RACH chunk, then the UEmonitors the PDCCH for RAR based on the RA-RNTI that is calculated atleast partly based on the index of RACH chunk where the RACH preamble(s)is transmitted.

In some embodiments, the RA-RNTI can be calculated based onslot/subframe index of PRACH, the index of RACH chunk in one PRACH andthe PRACH index within the slot/subframe or PRACH occasion. In onemethod (RA-RNTI method 1), the RA-RNTI is defined as RA_RNTI=ƒ₀(T_(i),F_(i), C_(i)) where ƒ₀ the function of calculating RA_RNTI, T_(i) is theindex of the subframe of PRACH, F_(i) is the index of the PRACH withinthat subframe and C_(i) is the RACH chunk index within that PRACH. Oneexample of function ƒ₀ can be: RA_RNTI=1+T_(i)+G×F_(i)+Q×C_(i). Thevalue of parameters G and Q can be configured by the gNB through systeminformation (e.g., SIB) or defined in the spec.

In some embodiments, the RA-RNTI can be calculated based on the index ofRACH symbol, the index of RACH chunk, PRACH index and slot indexinformation of PRACH. In one method (RA-RNTI method 2), the RA-RNTI isdefined as RA_RNTI=ƒ₁(T_(i), F_(i), C_(i), S_(i)) where ƒ₁ the functionof calculating RA_RNTI, T_(i) is the index of the subframe of PRACH,F_(i) is the index of the PRACH within that subframe and C_(i) is theRACH chunk index within that PRACH, S_(i) is the RACH symbol index.

In some embodiments, the UE is indicated to select which of the RA_RNTIcalculation methods for monitoring the PDCCH scheduling RAR, e.g.,implicitly based on the preamble transmission method the UE uses. Ifpreamble transmission method 1 is used, then the UE uses RA-RNTI method1; if preamble transmission method 2 is used, then the UE uses RA-RNTImethod 2.

In some embodiments, the timing of one RAR window is associated with onePRACH. In one method, the timing of one RAR window is associated withthe RACH chunk index within a selected PRACH. In this manner, the UE isconfigured to monitor and receive the RAR transmitted associated on theRACH chunk where the UE sends the preamble. One RAR window is associatedwith a RACH chunk index within a selected PRACH. In another methodwithin one PRACH. In this manner, the UE is configured to monitor andreceive the RAR transmission associated with the subset/group of RACHchunks where the UE sends the preamble. One RAR window is associatedwith a group of RACH chunk indices within a selected PRACH.

In some embodiments, the RAR can include the information of the RACHchunk and the RACH symbol indices where the preamble is detected and theinformation of UE Tx beam. The UE can use such information to assist theUE Tx beam selection for the transmission of RACH msg3 and otherfollowing UL transmission.

In some embodiments, a UE is configured with a method of transmittingRAR. The method of transmitting RAR can be configured through RACHconfiguration index.

FIG. 11 illustrates an example RAR occasion 1120 according toembodiments of the present disclosure. An embodiment of the RAR occasion1120 shown in FIG. 11 is for illustration only. One or more of thecomponents illustrated in FIG. 11 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

In some embodiments, the random access response (RAR) is sent through aTx beam sweeping methods. In each RAR occasion, there are S×H OFDMsymbols and each S contiguous OFDM symbols is one RAR chance. One ormore RAR could be transmitted within one RAR chance. The gNB utilizessame Tx beam on each RAR chance and sweeps the Tx beams over multipleRAR chance. An example of RAR occasion is shown in FIG. 11.

As illustrated in FIG. 11, one RAR occasion 1100 contains three RARchances 1111, 1112, and 1113 (e.g., RACH chances). Each RAR chance iscomprised of two contiguous OFDM symbols. The gNB utilizes same Tx beamon two OFDM symbols within on RAR chance and sweeps the Tx beams overRACH chances 1111, 1112, and 1113.

In some embodiments, the RAR occasion is transmitted periodically withperiodicity T_(RAR). In some embodiments, a UE is configured with one ormore of the following about RAR occasion transmission by the systeminformation channel: the periodicity T_(RAR) in terms of, for example,subframes, ms. The indices of subframes or time interval wherein RARoccasion may occur; number of OFDM symbols per RAR chance; number of RARchances per RAR occasion; and the indices of OFDM symbols used for RAR,in the subframe or time interval where the RAR occasion is transmitted.

In some embodiments, the UE is configured of the information of RARconfiguration through a RAR configuration index. The UE is configured tocalculate the RAR configuration based on the value of RAR configurationindex.

TABLE 3 RAR configuration Indices of RAR subframes Number of config-wherein OFDM symbol Number of OFDM symbol uration RAR is indices usedfor RAR in one RAR index mapped RAR chances chance 0 Subset 0 of k₀ H₀S₀ subframes 1 Subset 1 of k₁ H₁ S₁ subframe

In some embodiments, the UE is configured to receive the UE-specificconfiguration of reference signal for the beam measurement in RACH msg4.The reference signal can be called CSI-RS, BRS (beam RS), MRS(measurement/mobility RS). The term BRS may be used for the referencesignal, which does not exclude that the reference signal could be calledby other terms.

The UE-specific configuration of BRS for the beam measurementtransmitted in RACH msg4 includes one or more of the followings. In oneexample, the UE-specific configuration comprises number of OFDM symbolsand number of antenna ports in the BRS. In such example, the number ofOFDM symbols to map the BRS is explicitly indicated in theconfiguration. The number of antenna port is explicitly indicated in theconfiguration. In one instance, a 2-bit field is used to indicate thenumber of OFDM symbols. Four values of the 2-bit field indicate fourdifferent values of the number of OFDM symbols. In one instance, a 2-bitfield is used to indicate the number of antenna ports. Four values ofthe 2-bit field indicate four different values of the number of antennaports.

In another example, the UE-specific configuration comprises the beam IDconfiguration. In such example, the allocation of beam IDs to the OFDMsymbols and/or antenna ports of the BRS are configured here. In oneexample, one beam ID is allocated to per antenna port per OFDM symbol.In one instance, one beam ID is allocated per OFDM symbol.

In yet another example, the UE-specific configuration comprises the beamgrouping configuration for constrained measurement. In such example, thegNB configures the beam IDs into N_(g) beam groups and the UE isconfigured to make a constrained measurement on the beams. In suchexample, the beam grouping is configured through OFDM symbol index. Inone instance, the beam grouping is configured through BRS antenna portindex. In one instance, the beam grouping is configured through OFDMsymbol index and antenna port index.

In yet another example, the UE-specific configuration comprises beamcluster configuration. In such example, the gNB could configure N_(c)beam clusters and the UE is configured to measure beam-cluster-specificRSRP. In one instance, the beam cluster configuration is in terms ofreference signal OFDM symbol index. In one instance, the beam clusterconfiguration is in terms of antenna ports. In one example, the beamcluster configuration is in terms of BRS resource.

In yet another example, the UE-specific configuration comprises an RSRPcalculation method. In such example, the UE is configured to measurebeam-specific RSRP and cell-specific RSRP. In one instance, a 2-bit isused to indicate which RSRP(s) may be measured by the UE. In oneinstance, a 2-bit is used to indicate the method of calculating thecell-specific RSRP.

In some embodiments, procedure of the initial random access procedure isas following. In step 1, the UE receives the RACH configuration from thesystem information channel. In step 2, based on the preamble typeconfiguration in RACH configuration, the UE selects one preamblesequence: if preamble type is 0, the UE selects the preamble sequencewithout conveying Tx beam ID; and if preamble type is 1, the UE isconfigured to obtain the configuration information of mapping Tx beam IDto preamble sequence ID and then select one preamble sequence ID basedon this configuration and the Tx beam ID that corresponding to thestrongest RSRP of downlink SS and/or BRS signal.

In step 3, the UE selects one RACH chunk based on the RACHconfiguration. One example is that RACH configuration defines a mappingbetween RACH chunk and downlink OFDM symbols wherein the SS/PBCH/BRS aremapped, and the UE selects RACH chunk corresponding to the downlink OFDMsymbol where the UE measures the strongest RSRP of SS and/or BRS.

In step 4, the UE transmits the preamble sequence on the selected RACHchunk. Based on the RACH configuration, the UE could do Tx beam sweepingon the RACH symbols in the selected RACH chunk.

In step 5, if the preamble transmission is failed, the UE select theRACH chunk for the retransmission based on the RACH configuration asfollows. The UE re-transmit the preamble sequence on the selected RACHchunk with Tx power being increased with a configured step-size. In oneexample, if the mode of switch RACH chunk is to use the same RACH chunk,the UE use the same RACH chunk and increase the Tx power to retransmitthe preamble sequence. In another example, if the mode of switching RACHchunk is to calculate next RACH chunk index based on previous RACH chunkindex, the UE calculates the RACH chunk index based on the configuredcalculation method and previous RACH chunk index. In yet anotherexample, if the mode of switching RACH chunk is pseudo-random sequence,the UE generates pseudo-random sequence as configured and then calculatethe RACH chunk index for preamble retransmission.

In step 6, the UE is configured to detect the RAR based on the RACHconfiguration. In one example, if the RAR type is 0, i.e., RAR is sentin PDSCH indicated by a DCI with RA-RNTI, the UE is configured to detectDCI with RA-RNTI and then decode the scheduled PDSCH. In anotherexample, if the RAR type is 1, i.e. RAR is sent by Tx beam sweeping, theUE is configured to obtain the RAR Tx beam sweeping configuration fromthe system information channel and then the UE is configured to decodethe RAR from each RAR chance.

In step 7, the UE is configured to transmit msg3 according to thescheduling information delivered in RAR. In one example, if the UE isconfigured to include a Tx beam ID in msg3, the UE include a Tx beam IDwith the best RSRP in msg3.

In step 8, the UE is configured to receive the msg4.

FIG. 12 illustrates a flow chart of a method 1200 for RACH procedure, asmay be performed by a UE (111-116 as illustrated in FIG. 1), accordingto embodiments of the present disclosure. An embodiment of the method1200 shown in FIG. 12 is for illustration only. One or more of thecomponents illustrated in FIG. 12 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 12, the method 1200 begins at step 1205. In step 1205,the UE receives, from a base station (BS), random access channel (RACH)configuration information including RACH chunk information correspondingto at least one antenna beam including a beam identifier (ID). In step1205, the RACH configuration information comprises at least one of theindex of the slot, the index of the RACH chunk, partitioninginformation, beam sweeping information, a preamble type, orretransmission information.

Next, the UE in step 1210 determines an RACH chunk based on the RACHconfiguration information received from the BS. In some embodiments, theUE in step 1210 further determines an RACH occasion for the RACHpreamble by re-selecting other RACH chunks each of which includes RACHsymbols based on the RACH chunk information or performing a powerramping that adjusts a transmit power of the RACH preamble.

In some embodiments, the UE in step 1210 maps, based on the RACHconfiguration information, downlink signal symbols to RACH chunks, thedownlink signal symbols transmitted on at least one of synchronizationsignal (SS), a broadcasting signal on a physical broadcasting channel(PBCH), or a beam reference signal (BRS).

In some embodiments, the UE in step 1210, maps, based on the RACHconfiguration information, downlink signal symbols to a subset of RACHpreamble sequences, the downlink signal symbols being conveyed by atleast one of synchronization signal (SS), a broadcasting signal on aphysical broadcasting channel (PBCH), or a beam reference signal (BRS).

Subsequently, in step 1215, the UE transmits, to the BS, an RACHpreamble on the determined RACH chunk according to the RACHconfiguration information associated with the beam ID. In someembodiments, the UE in step 1215 identifies dedicated resources for theBS to apply the at least one antenna beam, transmits the RACH preambleon dedicated resources over which the at least one antenna beam isapplied to receive signals, and transmits the RACH preamble over RACHsymbols in the determined RACH chunk over the at least one antenna beamthat is swept to receive signals.

In some embodiments, the UE in step 1215 transmits the RACH preambleincluding the beam ID using the RACH chunk from the RACH chunks mappedto at least one downlink signal symbol selected. In some embodiments,the UE in step 1215 transmits the RACH preamble including the beam IDusing an RACH preamble sequence from the subset of RACH preamblesequences mapped to at least one downlink signal symbol selected.

Finally, the UE in step 1220 receives, from the BS, an RACH response(RAR) corresponding to the transmitted RACH preamble and a downlinkchannel for an RAR transmission. In step 1220, a random access-radionetwork temporary identification (RA-RNTI) is calculated based on anindex of a slot and an index of the RACH chunk on which the RACHpreamble is transmitted.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

None of the description in this application should be read as implyingthat any particular element, step, or function is an essential elementthat must be included in the claims scope. The scope of patented subjectmatter is defined only by the claims. Moreover, none of the claims areintended to invoke 35 U.S.C. § 112(f) unless the exact words “means for”are followed by a participle.

What is claimed is:
 1. A user equipment (UE) for random access operationin a wireless communication system, the UE comprising: at least onetransceiver configured to receive, from a base station (BS),configuration information indicating a random access channel (RACH)occasion that includes at least one RACH chunk, the at least one RACHchunk including at least one RACH symbol; and at least one processorconfigured to determine a RACH chunk from the at least one RACH chunkand the RACH occasion based on the configuration information receivedfrom the BS, wherein the transceiver is further configured to transmit,to the BS, a RACH preamble on the determined RACH chunk according to theconfiguration information, and wherein the processor is furtherconfigured to: use an index of the RACH occasion and an index of theRACH chunk determined for transmitting the RACH preamble to calculate arandom access radio network temporary identification (RA-RNTI); and usethe calculated RA-RNTI to detect a RACH response from the BS.
 2. The UEof claim 1, wherein: the at least one processor is further configuredto: determine to re-transmit the RACH preamble if the RACH response withthe calculated RA-RNTI is not received; and select a second RACH chunkthat is different from the determined RACH chunk, and the transceiver isfurther configured to re-transmit the RACH preamble on the selectedsecond RACH chunk with a same transmit power of as the prior transmittedRACH preamble.
 3. The UE of claim 1, wherein: the at least one processoris further configured to: determine to re-transmit the RACH preamble ifthe RACH response with the calculated RA-RNTI is not received; anddetermine to use a same RACH chunk for the RACH preamble re-transmissionas the determined RACH chunk and to increase a transmit power for theRACH preamble re-transmission by a power offset, and the transceiver isfurther configured to re-transmit the RACH preamble on the same RACHchunk and with the increased transmit power.
 4. The UE of claim 1,wherein the at least one processor is further configured to calculatethe RA-RNTI as:RA_RNTI=ƒ_(i)(T _(i) ,F _(i) ,C _(i) ,S _(i)) where RA_RNTI is thecalculated RA-RNTI, ƒ_(i) is a function of calculating the RA-RNTI,T_(i) is an index of a subframe where the determined RACH occasion is,F_(i) is an index of the determined the RACH occasion, C_(i) is an indexof the determined RACH chunk, and S_(i) is an index of a RACH symbolwithin the determined RACH chunk.
 5. The UE of claim 1, wherein: the atleast one processor is configured with a method of BS beam sweeping overRACH symbols within one RACH chunk, and the processor is furtherconfigured to select a method to calculate the RA-RNTI according to themethod of BS beam sweeping for the determined RACH chunk in which theRACH preamble is transmitted.
 6. The UE of claim 1, wherein: the atleast one processor is further configured to map, based on theconfiguration information, downlink signal symbols to RACH chunks, thedownlink signal symbols transmitted on at least one of synchronizationsignal (SS), a broadcasting signal on a physical broadcasting channel(PBCH), or a beam reference signal (BRS); and the transceiver is furtherconfigured to transmit the RACH preamble including a beam ID using theRACH chunk from the RACH chunks mapped to at least one downlink signalsymbol selected.
 7. The UE of claim 1, wherein: the at least oneprocessor is further configured to map, based on the configurationinformation, downlink signal symbols to a subset of RACH preamblesequences, the downlink signal symbols being conveyed by at least one ofsynchronization signal (SS), a broadcasting signal on a physicalbroadcasting channel (PBCH), or a beam reference signal (BRS); and thetransceiver is further configured to transmit the RACH preambleincluding a beam ID using a RACH preamble sequence from the subset ofRACH preamble sequences mapped to at least one downlink signal symbolselected.
 8. A base station (BS) for random access operation in awireless communication system, the BS comprising: at least one processorconfigured to determine configuration information indicating a randomaccess channel (RACH) occasion that includes at least one RACH chunk,the at least one RACH chunk including at least one RACH symbol; at leastone transceiver configured to: transmit, to a user equipment (UE), theconfiguration information indicating the RACH occasion that includes theat least one RACH chunk; and receive, from the UE, a RACH preamble onthe RACH chunk according to the configuration information, wherein theprocessor is configured to use an index of the RACH occasion and anindex of the RACH chunk on which the RACH preamble is received tocalculate a random access radio network temporary identification(RA-RNTI); and use the calculated RA-RNTI to indicate a RACH response tothe BS.
 9. The BS of claim 8, wherein the transceiver is furtherconfigured to receive a re-transmission of the RACH preamble on a secondRACH chunk if the RACH response with the calculated RA-RNTI is notreceived from the BS, the second RACH chunk different that the RACHchunk, the re-transmission made with a same transmit power of as theprior transmission of the RACH preamble.
 10. The BS of claim 8, whereinthe transceiver is further configured to receive a re-transmission ofthe RACH preamble on a same RACH chunk as the RACH chunk for the priortransmission of the RACH preamble if the RACH response with thecalculated RA-RNTI is not received from the BS, the re-transmission madewith a transmit power increased by a power offset from the priortransmission of the RACH preamble.
 11. The BS of claim 8, wherein theRA-RNTI is calculated as:RA_RNTI=ƒ_(i)(T _(i) ,F _(i) ,C _(i) ,S _(i)) where RA_RNTI is thecalculated RA-RNTI, ƒ_(i) is a function of calculating the RA-RNTI,T_(i) is an index of a subframe where the RACH occasion is, F_(i) is anindex of the RACH occasion, C_(i) is an index of the RACH chunk, andS_(i) is an index of a RACH symbol within the RACH chunk.
 12. The BS ofclaim 8, wherein: the UE is configured with a method of BS beam sweepingover RACH symbols within one RACH chunk, and the UE selects a method tocalculate the RA-RNTI according to the method of BS beam sweeping forthe RACH chunk in which the RACH preamble is transmitted.
 13. The BS ofclaim 8, wherein: the at least one processor is further configured tomap, based on the configuration information, downlink signal symbols toRACH chunks, the downlink signal symbols transmitted on at least one ofsynchronization signal (SS), a broadcasting signal on a physicalbroadcasting channel (PBCH), or a beam reference signal (BRS); and thetransceiver is further configured to receive the RACH preamble includinga beam ID using the RACH chunk from the RACH chunks mapped to at leastone downlink signal symbol selected.
 14. The BS of claim 8, wherein: theat least one processor is further configured to map, based on theconfiguration information, downlink signal symbols to a subset of RACHpreamble sequences, the downlink signal symbols being conveyed by atleast one of synchronization signal (SS), a broadcasting signal on aphysical broadcasting channel (PBCH), or a beam reference signal (BRS);and the transceiver is further configured to receive the RACH preambleincluding a beam ID using a RACH preamble sequence from the subset ofRACH preamble sequences mapped to at least one downlink signal symbolselected.
 15. A method of user equipment (UE) for random accessoperation in a wireless communication system, the method comprising:receiving, from a base station (BS), configuration informationindicating a random access channel (RACH) occasion that includes atleast one RACH chunk, the at least one RACH chunk including at least oneRACH symbol; determining a RACH chunk from the at least one RACH chunkand the RACH occasion based on the configuration information receivedfrom the BS, transmitting, to the BS, a RACH preamble on the determinedRACH chunk according to the configuration information; using an index ofthe RACH occasion and an index of the RACH chunk determined fortransmitting the RACH preamble to calculate a random access radionetwork temporary identification (RA-RNTI); and using the calculatedRA-RNTI to detect a RACH response from the BS.
 16. The method of claim15, further comprising: determining to re-transmit the RACH preamble ifthe RACH response with the calculated RA-RNTI is not received; selectinga second RACH chunk that is different from the determined RACH chunk;and re-transmitting the RACH preamble on the selected second RACH chunkwith a same transmit power of as the prior transmitted RACH preamble.17. The method of claim 15, further comprising: determining tore-transmit the RACH preamble if the RACH response with the calculatedRA-RNTI is not received; determining to use a same RACH chunk for theRACH preamble re-transmission as the determined RACH chunk and toincrease a transmit power for the RACH preamble re-transmission by apower offset; and re-transmitting the RACH preamble on the same RACHchunk and with the increased transmit power.
 18. The method of claim 15,further comprising: calculating the RA-RNTI as:RA_RNTI=ƒ_(i)(T _(i) ,F _(i) ,C _(i) ,S _(i)) where RA_RNTI is thecalculated RA-RNTI, ƒ_(i) is a function of calculating the RA-RNTI,T_(i) is an index of a subframe where the determined RACH occasion is,F_(i) is an index of the determined the RACH occasion, C_(i) is an indexof the determined RACH chunk, and S_(i) is an index of a RACH symbolwithin the determined RACH chunk.
 19. The method of claim 15, wherein:the UE is configured with a method of BS beam sweeping over RACH symbolswithin one RACH chunk, and the UE selects a method to calculate theRA-RNTI according to the method of BS beam sweeping for the determinedRACH chunk in which the RACH preamble is transmitted.
 20. The method ofclaim 15, further comprising: mapping, based on the configurationinformation, downlink signal symbols to a subset of RACH preamblesequences, the downlink signal symbols being conveyed by at least one ofsynchronization signal (SS), a broadcasting signal on a physicalbroadcasting channel (PBCH), or a beam reference signal (BRS); andtransmitting the RACH preamble including a beam ID using a RACH preamblesequence from the subset of RACH preamble sequences mapped to at leastone downlink signal symbol selected.